Solutions Important Questions for NEET Chemistry 2027 PDF Download (Login Required)

1. Multiple choice questions.

Q1. Which of the following statements is correct about an ideal solution?

• (a) $\Delta H_{mix} = 0$, $\Delta V_{mix} = 0$
• (b) $\Delta H_{mix} \neq 0$, $\Delta V_{mix} = 0$
• (c) $\Delta H_{mix} = 0$, $\Delta V_{mix} \neq 0$
• (d) $\Delta H_{mix} \neq 0$, $\Delta V_{mix} \neq 0$

Answer: (a) $\Delta H_{mix} = 0$, $\Delta V_{mix} = 0$

Q2. The molality of a solution prepared by dissolving 18 g of glucose (molar mass = 180 g/mol) in 500 g of water is:

• (a) 0.1 mol/kg
• (b) 1 mol/kg
• (c) 0.2 mol/kg
• (d) 2 mol/kg

Answer: (a) 0.1 mol/kg

Q3. Which property is not a colligative property?

• (a) Elevation of boiling point
• (b) Depression of freezing point
• (c) Relative lowering of vapour pressure
• (d) Increase in viscosity

Answer: (d) Increase in viscosity

Q4. According to Raoult’s Law, the vapour pressure of a solution containing a non-volatile solute is:

• (a) Equal to pure solvent vapour pressure
• (b) Higher than pure solvent
• (c) Lower than pure solvent
• (d) Same as the solute

Answer: (c) Lower than pure solvent

Q5. In the case of abnormal molar mass, the value of van’t Hoff factor (i) is:

• (a) Always 1
• (b) Not equal to 1
• (c) Always less than 1
• (d) Always greater than 1

Answer: (b) Not equal to 1

2. Very Short Answer (VSA).

Q1. Define molality.

Answer: Molality (m) is the number of moles of solute dissolved in 1 kg (1000 g) of solvent.

Q2. What does van’t Hoff factor indicate?

Answer: Van’t Hoff factor (i) indicates the extent of association or dissociation of solute molecules in a solution.

Q3. Name any one colligative property.

Answer: Depression of freezing point is a colligative property.

Q4. What is the mole fraction of water in a solution containing 10 moles of water and 1 mole of NaCl?

Answer: The mole fraction of water is $10/(10+1) = 10/11$.

Q5. Write the mathematical expression for Raoult’s Law.

Answer: $P_1 = X_1 P_1^0$, where $P_1$ is the vapour pressure, $X_1$ is the mole fraction, $P_1^0$ is vapour pressure of pure solvent.

3. Short Answer Questions.

Q1. A solution contains 5 g of urea $(\mathrm{NH_2CONH_2})$ in 100 g of water. Calculate the lowering of vapour pressure if vapour pressure of pure water at 298 K is 23.8 mm Hg. (Molar mass of urea = 60 g/mol)

Answer:

1. Moles of urea = $5/60 = 0.083$ mol.
2. Moles of water = $100/18 = 5.56$ mol.
3. Mole fraction of urea = $0.083/(0.083+5.56) = 0.0147$.
4. Relative lowering = mole fraction of solute = $0.0147$.
5. Lowering = $23.8 \times 0.0147 = 0.349$ mm Hg.

Q2. Explain why a non-volatile solute lowers the vapour pressure of a solvent.

Answer: A non-volatile solute reduces the number of solvent molecules at the liquid surface, decreasing the rate of evaporation and thus lowering the vapour pressure. This effect is proportional to the solute's mole fraction, as stated by Raoult’s Law.

Q3. What is abnormal molecular mass? How does van’t Hoff factor correct it?

Answer: Abnormal molecular mass arises when solute molecules associate or dissociate in solution, leading to incorrect molar mass calculation via colligative properties. The van’t Hoff factor (i) adjusts the observed values to correct the calculated molar mass.

Q4. How can you determine the molar mass of a solute from elevation of boiling point?

Answer: Molar mass can be calculated using: $\Delta T_b = K_b \cdot m$, where $m$ is molality. Knowing $\Delta T_b$ (boiling point elevation), $K_b$ (ebullioscopic constant), solvent mass, and solute mass, we rearrange to find the solute's molar mass.

Q5. State the difference between ideal and non-ideal solutions with one example each.

Answer: Ideal solutions obey Raoult's Law at all concentrations (e.g., benzene and toluene) with zero enthalpy and volume changes on mixing. Non-ideal solutions deviate from Raoult’s Law (e.g., acetone and chloroform) and exhibit enthalpy or volume change.

4. True or False Questions.

Q1. The value of van’t Hoff factor for glucose is unity.

Answer: True

Q2. Depression of freezing point does not depend on the nature of solute.

Answer: True

Q3. An increase in the number of solute particles increases osmotic pressure.

Answer: True

Q4. A solution showing negative deviation from Raoult’s law will have strong intermolecular attraction among components.

Answer: True

Q5. The mole fraction is always less than one.

Answer: True

3. Fill in the Blanks Questions.

Q1. The osmotic pressure of a solution is proportional to the _______ of the solute particles.

Answer: number

Q2. For an electrolyte which dissociates completely, van’t Hoff factor is _______ than one.

Answer: greater

Q3. The percentage by mass of a solution is calculated as (mass of solute / mass of solution) × _______ .

Answer: 100

Q4. When a non-volatile solute is added to a solvent, the vapour pressure of the solution becomes _______ than that of the pure solvent.

Answer: lower

Q5. The unit of molarity is _______ .

Answer: mol/L

Advantages of Studying Solutions for NEET Chemistry

Understanding concepts like molality, molarity, and mole fraction helps you solve NEET Chemistry problems easily. These core topics are frequently asked and are important for quick calculations. Practice ensures confidence and accuracy in the exam.

Topics like Raoult’s Law, colligative properties, and vapour pressure form the backbone of solution chemistry questions. Clearing these fundamentals can help you approach tricky questions with clarity and score higher in NEET.

At Vedantu, we focus on stepwise answers which build your basics and improve your speed. Stay regular with practice of important questions to get a better grip on the chapter and boost your NEET Chemistry performance.